When was the frozen yogurt invented?

The concept of frozen yogurt can be traced back to 1919 when a Bulgarian microbiologist named Stamen Grigorov discovered a bacteria called Lactobacillus bulgaricus in a yogurt made by local shepherds. This bacteria was able to ferment milk into a product that was similar to yogurt. Frozen yogurt was eventually developed in the 1970s as a healthier alternative to ice cream.